Production of bio-based liquefied petroleum gas

ABSTRACT

The disclosure provides methods for the production of liquefied petroleum gas from sustainable feedstocks, including methods comprising conversion of alcohols produced by gas fermentation for the production of propane and/or butane.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims the benefit of U.S. Provisional Application Nos.62/798,264, 62/860,369 and 62/887,125 filed Jan. 29, 2019, Jun. 12,2019, and Aug. 15, 2019, respectively, the contents of which are herebyincorporated by reference.

BACKGROUND

There is growing interest in using renewable resources for energy andchemical production. Carbon dioxide (CO₂) accounts for about 76% ofglobal greenhouse gas emissions from human activities, with methane(16%), nitrous oxide (6%), and fluorinated gases (2%) accounting for thebalance (United States Environmental Protection Agency). The majority ofCO₂ comes from the burning of fossil fuels to produce energy, althoughindustrial and forestry practices also emit CO₂ into the atmosphere.Reduction of greenhouse gas emissions, particularly CO₂, is critical tohalt the progression of global warming and the accompanying shifts inclimate and weather.

It has long been recognized that catalytic processes, such as theFischer-Tropsch process, may be used to convert gases comprising carbondioxide (CO₂), carbon monoxide (CO), and/or hydrogen (H₂), such asindustrial waste gas or syngas, into a variety of fuels and chemicals.Recently, however, gas fermentation has emerged as an alternativeplatform for the biological fixation of such gases. In particular,C1-fixing microorganisms have been demonstrated to convert gasescomprising CO₂, CO, CH₄, and/or H₂ into products such as ethanol and2,3-butanediol.

Liquefied petroleum gas (LPG) is primarily composed of around 98%propane and/or butane with some allowable amounts of olefins such aspropylene or butenes, other light hydrocarbons such as ethane, and/orheavier components. The exact composition varies by region. For example,LPG in the US is primarily propane, while in Europe it can reach up to80% butane—there is considerable variation from country to country. Theenergy content of LPG ranges from about 49 to 50 MJ/kg or 25 to 28MJ/liter.

Typically, LPG is produced from gas wells, byproduct gas from oil wells,and off-gas from refinery processes (FIG. 1 ).

In current bio-based LPG production methods (FIG. 2 ), thehydroprocessed esters and fatty acids (HEFA) process is used to converttri-glycerides to primarily diesel range materials. The backbone oftri-glycerides is glycerol, which is a 3-carbon tri-alcohol. During theinitial hydrogenolysis step of the HEFA process, the glycerol backboneis converted to propane as a byproduct. Although this propane qualifiesas bio-based LPG because it has been produced from a waste oil, thelimited amount of available waste or sustainably produced oilssignificantly limits the amount of LPG that can be produced in thismanner (typically representing only about 5% of the starting carbon).

SUMMARY

The disclosure provides methods for producing liquefied petroleum gasfrom alcohols produced from bio-based or sustainable feedstocks such aswaste gases, municipal solid waste (MSW), or refinery/chemical plantwaste streams.

In a first aspect of the invention, the disclosure provides methods ofproducing liquefied petroleum gas comprising contacting a feed streamcomprising a C3 alcohol, such as isopropanol and/or 1-propanol, and/or aC4 alcohol, such as butanol or an isomer of butanol, with one or morecatalysts to produce a product stream comprising propane and/or butane,wherein the dehydration feed stream is a product of microbialfermentation of a gaseous substrate. In some embodiments, the one ormore catalysts comprise a dehydration catalyst and/or a hydrogenationcatalyst. In some embodiments, the dehydration catalyst is selected fromthe group consisting of acidic alumina, aluminum phosphate,silica-alumina phosphate, amorphous silica-alumina, aluminosilicate,zirconia, sulfated zirconia, tungstated zirconia, tungsten carbide,molybdenum carbide, titania, sulfated carbon, phosphated carbon,phosphated silica, phosphated alumina, acidic resin, heteropolyacid,inorganic acid, and any combination thereof. In some embodiments, thehydrogenation catalyst comprises a Ni-alumina, Pd—C, Raney-Ni, Co, or Ptcatalyst, or any combination thereof.

In some embodiments of the first aspect, one reactor comprises thedehydration catalyst and/or the hydrogenation catalyst. In someembodiments of the first aspect, one catalyst comprises functionality ofthe dehydrogenation catalyst and functionality of the hydrogenationcatalyst. In some embodiments of the first aspect, a dehydration reactorcomprises the dehydration catalyst and a hydrogenation reactor comprisesthe hydrogenation catalyst.

In some embodiments of the first aspect, the method comprises (a)contacting, in the dehydration reactor, the feed stream comprising theC3 alcohol and/or the C4 alcohol with the dehydration catalyst toproduce an effluent stream comprising a C3 alkene, such as propene,and/or a C4 alkene, such as butene, an isomer of butene, or butadiene;and (b) contacting, in the hydrogenation reactor, the effluent streamcomprising propene and/or butene with hydrogen and the hydrogenationcatalyst to produce the product stream comprising propane and/or butane.

In some embodiments, the dehydration reactor operates at a temperatureof from about 100° C. to about 500° C., of from about 350° C. to about450° C., or of from about 375° C. to about 425° C. In some embodiments,the dehydration reactor operates at a pressure of from about 0.2 MPa toabout 2 MPa, of from about 0.2 MPa to about 1 MPa, or of from about 0.2MPa to about 0.7 MPa. In some embodiments, the dehydration reactoroperates at a weight hourly space velocity (whsv) of from about 1 h⁻¹ toabout 10 h⁻¹, of from about 2 h⁻¹ to about 8 h⁻¹, or of from about 0.5h⁻¹ to about 2 h⁻¹.

In some embodiments of the first aspect, the hydrogenation reactoroperates at a temperature of less than about 400° C., of less than about250° C., or of about 100° C. to about 150° C. In some embodiments, thehydrogenation reactor operates at a pressure above about 1.7 MPa (about17 barg). In some embodiments, the hydrogenation reactor operates at apressure above about 1.7 MPa, of about 0.7 MPa to about 8.2 MPa, ofabout 0.7 MPa to about 2.0 MPa, or of about 1.0 MPa to about 2.0 MPa.

In a second aspect of the invention, the disclosure provides methods ofproducing liquefied petroleum gas comprising: (a) contacting, in adehydration reactor, a dehydration feed stream comprising ethanol with acatalyst to produce a first reactor effluent stream comprising ethylene;wherein the dehydration feed stream is a product of microbialfermentation of a gaseous substrate; (b) contacting, in a dimerizationreactor, the first reactor effluent stream with a catalyst to produce asecond reactor effluent stream comprising butene; and (c) contacting, ina hydrogenation reactor, the second reactor effluent stream and hydrogenwith a catalyst to produce a product stream comprising butane.

In some embodiments, the dehydration reactor operates at a temperatureof from about 100° C. to about 500° C., of from about 350° C. to about450° C., or of from about 375° C. to about 425° C. In some embodiments,the dehydration reactor operates at a pressure of from about 0.2 MPa toabout 2 MPa, of from about 0.2 MPa to about 1 MPa, or of from about 0.2MPa to about 0.7 MPa. In some embodiments, the dehydration reactoroperates at a whsv of from about 1 h⁻¹ to about 10 h⁻¹, of from about 2h⁻¹ to about 8 h⁻¹, or of about 0.5 h⁻¹ to about 2 h⁻¹. In someembodiments, the dehydration reactor comprises a dehydration catalystselected from the group consisting of acidic alumina, aluminumphosphate, silica-alumina phosphate, amorphous silica-alumina,aluminosilicate, zirconia, sulfated zirconia, tungstated zirconia,tungsten carbide, molybdenum carbide, titania, sulfated carbon,phosphated carbon, phosphated silica, phosphated alumina, acidic resin,heteropolyacid, inorganic acid, and any combination thereof.

In some embodiments of the second aspect, the dimerization reactoroperates at a temperature of from about 10° C. to about 150° C., of fromabout 24° C. to about 135° C., of from about 38° C. to about 121° C., orof from about 50° C. to about 60° C. In some embodiments, thedimerization reactor operates at a pressure of about 0.7 MPa to about6.9 MPa, of about 2.4 MPa to about 4.8 MPa, of about 2.8 MPa to about3.4 MPa, or of about 2.0 MPa to about 2.7 MPa. In some embodiments, thedimerization reactor comprises an ionic liquid catalyst. In someembodiments, the dimerization reactor further comprises a co-catalyst orpromoter. In some embodiments, the dimerization reactor comprises aTi(IV)/AlEt₃ catalyst.

In some embodiments of the second aspect, the hydrogenation reactoroperates at a temperature of less than about 400° C., of less than about250° C., or of about 100° C. to about 150° C. In some embodiments, thehydrogenation reactor operates at a pressure above about 1.7 MPa (about17 bar). In some embodiments, the hydrogenation reactor operates at apressure above about 1.7 MPa, of about 0.7 MPa to about 8.2 MPa, ofabout 0.7 MPa to about 2.0 MPa, or of about 1.0 MPa to 2.0 MPa. In someembodiments, the hydrogenation reactor comprises a Ni-alumina, Pd—C,Raney-Ni, Co, or Pt catalyst, or any combination thereof.

In a third aspect of the invention, the disclosure provides methods ofproducing liquefied petroleum gas comprising: (a) contacting, in acarbonylation reactor, a carbonylation feed stream comprising ethanoland carbon monoxide with a catalyst to produce a first reactor effluentstream comprising propionic acid; wherein the carbonylation feed streamis a product of microbial fermentation of a gaseous substrate; and (b)contacting, in a hydrogenation reactor, the first reactor effluentstream and hydrogen with a catalyst to produce a product streamcomprising propane.

In some embodiments of the third aspect, the carbonylation feed streamcomprises 1-75% water by weight. In some embodiments, the carbonylationreactor operates at a temperature of about 150° C. to about 250° C. orof about 180° C. to about 225° C. In some embodiments, the carbonylationreactor operates at a carbon monoxide partial pressure of about 0.2 MPato about 3.0 MPa, of about 0.2 MPa to about 1.0 Mpa, or of about 0.2 MPato about 0.3 MPa. In some embodiments, the carbonylation reactorcomprises a Rh carbonyl catalyst with ethyl and iodide ligands.

In some embodiments of the third aspect, the hydrogenation reactoroperates at a temperature of about 130° C. to about 200° C., of about140° C. to about 190° C., of about 150° C. to about 180° C., or of about150° C. to about 170° C. In some embodiments, the hydrogenation reactoroperates at a pressure of about 2.0 MPa to 4.0 MPa, of about 2.5 MPa toabout 3.5 MPa, or of about 2.7 to about 3.3 MPa. In some embodiments,the hydrogenation reactor comprises a Pd/Re/C catalyst.

The invention further provides a liquified petroleum gas productproduced by the methods disclosed herein.

Specific embodiments of the disclosure will become evident from thefollowing more detailed description of certain embodiments and theclaims.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 shows the conventional route to LPG production, in which LPG istypically prepared by refining petroleum or “wet” natural gas, and isthus derived from fossil fuel sources, being manufactured during therefining of petroleum (crude oil), or extracted from petroleum ornatural gas streams as they emerge from the ground. In some cases, C2-C4streams refined from fossil fuel sources are highly contaminated priorto clean-up.

FIG. 2 shows conventional bio-based LPG production, in which propane isproduced as a byproduct of triglyceride cracking (of, for example,vegetable oil/tallow sources) as fatty acids are cleaved from theglycerol backbone. Typically, propane represents only about 5% ofstarting carbon when produced in this manner.

FIG. 3A shows an aspect of LPG production of the disclosure bydehydration/hydrogenation of C3-C4 alcohols in a single reactor. FIG. 3Bshows an aspect of LPG production of the disclosure bydehydration/hydrogenation of C3-C4 alcohols in two separate reactors.

FIG. 4 shows an aspect of LPG production of the disclosure bydehydration/dimerization/hydrogenation of ethanol.

FIG. 5 shows an aspect of LPG production of the disclosure bycarbonylation/hydrogenation of ethanol.

DETAILED DESCRIPTION

Provided herein are methods for producing liquefied petroleum gas (LPG)from alcohols that are, in some embodiments, produced from bio-based orsustainable feedstocks such as waste gases, municipal solid waste (MSW),or refinery/chemical plant waste streams. The disclosed methods providea route to LPG production while, in some embodiments, advantageouslyreducing greenhouse gas (GHG) emissions.

In a first route, schematically illustrated in FIG. 3A and FIG. 3B, a C3alcohol (e.g., isopropanol) and a C4 alcohol (e.g., butanol) areproduced by gas fermentation. C3-C4 alcohols can be produced eitherindividually or in a combined manner using one or more bioreactors. Thealcohols produced in this manner can be purified using fractionation,extraction, membrane separation, or any other commonly used separationtechnique.

In some embodiments, the method for producing liquefied petroleum gascomprises contacting, in a single reactor, a feed stream comprising aC3-C4 alcohols with a catalyst or combination of catalysts to produce areactor effluent stream comprising propane and/or butane. Thehydrogenation reactor may be operated at a temperature of about 300° C.,a pressure of about 0.5 MPa, and a liquid hourly space velocity of about1 h⁻¹. The hydrogenation catalyst may be a Ni or Pd catalyst. See, e.g.,Grabowski et al., Applied Catalysis A: General 125: 129-144, 1995.

In some embodiments, C3-C4 alcohols are fed to one or more dehydrationreactors using a suitable catalyst such as alumina. In some embodiments,dehydration is performed at, for example, around 400° C. and around 0.5MPa of pressure. In some embodiments, once propene (propylene) and/orbutene have been produced, they can be hydrogenated with any suitablecatalyst, for example a Ni/alumina catalyst such as Ni-0750 E from BASFor Criterion KL6565, or a Pd/C catalyst such as JM 10R39. This processcan be carried out in a liquid phase, vapor phase, or trickle bedreactor. In some embodiments, this process is carried out in a tricklebed and/or vapor phase reactor. In some embodiments, hydrogenation isperformed at around 115° C. and around 1.0 MPa of pressure. However, thereaction can be carried out at any suitable pressure; in someembodiments, pressures above 250 psig are employed to maximize thehydrogenation rate. The reaction can be carried out at any suitabletemperature with favorable equilibria for the saturation reaction,generally less than 400° C., and more favorably less than 250° C. Thefinal step will be the separation of any remaining hydrogen andunreacted olefin from the product LPG, and recycling the hydrogen/olefinstream back to the hydrogenation reaction.

Thus, in a first aspect, the disclosure provides methods of producingliquefied petroleum gas comprising contacting a feed stream comprising aC3 alcohol and/or a C4 alcohol, such as isopropanol, 1-propanol, and/orbutanol, with one or more catalysts to produce a product streamcomprising propane and/or butane, wherein the dehydration feed stream isa product of microbial fermentation of a gaseous substrate. The firstaspect further provides methods of producing liquefied petroleum gascomprising: (a) contacting, in a dehydration reactor, a dehydration feedstream comprising a C3 alcohol and/or C4 alcohol with a catalyst toproduce a first reactor effluent stream comprising propene and/orbutene; and (b) contacting, in a hydrogenation reactor, the firstreactor effluent stream and hydrogen with a catalyst to produce aproduct stream comprising propane and/or butane.

A second route, schematically illustrated in FIG. 4 , can be used toconvert ethanol to ethylene, dimerize to butene, and then hydrogenate tobutane. Ethanol can be produced in a variety of ways, most commonly byfermentation routes. The dehydration of ethanol to ethylene is awell-known commercial process that uses commercially available catalystssuch as alumina or zeolitic materials at conditions such as 400° C. at0.5 MPa and 0.5-2 h⁻¹ whsv. The ethylene produced can be purified byfractionation, extraction, membrane separation, or another method toproduce a product of sufficient purity to be dimerized. The dimerizationcan be done in a homogeneous system such as the well-known Alphabutolprocess or done using a heterogeneous catalyst as described in Metzgeret al., ACS Central Science 2: 148-153, 2016. Once the 1-butene (orother butene isomer) has been produced, it can be hydrogenated asdescribed for route 1 above, such as at 100° C. and 1.0 MPa with a Ni orPd catalyst. Advantageously, this route can be adapted to consumesustainable ethanol feedstocks, which are readily available.

Thus, in a second aspect, the disclosure provides methods of producingliquefied petroleum gas comprising: (a) contacting, in a dehydrationreactor, a dehydration feed stream comprising ethanol with a catalyst toproduce a first reactor effluent stream comprising ethylene; wherein thedehydration feed stream is a product of microbial fermentation of agaseous substrate; (b) contacting, in a dimerization reactor, the firstreactor effluent stream with a catalyst to produce a second reactoreffluent stream comprising butene; and (c) contacting, in ahydrogenation reactor, the second reactor effluent stream and hydrogenwith a catalyst to produce a product stream comprising butane.

In a third route, schematically illustrated in FIG. 5 , ethanol can beproduced as described for the previous route. The ethanol can then becarbonylated using CO at 0.2-0.3 MPa (2-3 barg) pressure (higherpressures are also feasible) at 150-250° C. and 2500 h⁻¹ gas hourlyspace velocity (ghsv) using a Rh carbonyl catalyst with ethyl and iodideligands. The reaction is carried out in a homogeneous reaction spargingthe CO through the reactor with hydrostatic or mechanical mixing. Theproduct is propionic acid, which can be purified by a method not limitedto extraction, phase separation, and fractionation. The propionic acidthus produced can be hydrogenated to produce propane and water, whichcan be easily separation by condensing the water or using fractionation.Example conditions for the final step are 160° C. at 3.0 MPa hydrogenwith a Pt—Re/Carbon heterogeneous catalyst. See, e.g., Ullrich andBreit, 2018, ACS Catal. 8: 785-89.

Thus, in a third aspect, the disclosure provides methods of producingliquefied petroleum gas comprising: (a) contacting, in a carbonylationreactor, a carbonylation feed stream comprising ethanol with carbonmonoxide with a catalyst to produce a first reactor effluent streamcomprising propionic acid; wherein the carbonylation feed stream is aproduct of microbial fermentation of a gaseous substrate; and (b)contacting, in a hydrogenation reactor, the first reactor effluentstream and hydrogen with a catalyst to produce a product streamcomprising propane.

For any of the disclosed aspects, any of the feed streams and/oreffluent streams may be purified or enriched in any of the desiredcomponents using any method or combination of methods known in the art,including, for example, extraction, membrane separation, fractionation,fractional distillation, evaporation, pervaporation, gas stripping,phase separation, and extractive fermentation. In some embodiments, theremoved fraction is recycled back to a reactor from which an effluentstream came, especially in cases where the removed fraction comprisesreagents consumed within the reactor.

Dehydration

In some embodiments of the disclosed aspects, ethanol, propanols, andbutanols obtained by biochemical and/or thermochemical production routesare converted into their corresponding olefins by contacting thealcohols with a dehydration catalyst under appropriate conditions.Typical dehydration catalysts that convert alcohols such as ethanol,isopropanol, and butanol into ethylene, propylene, and butene(s) includevarious acid treated and untreated alumina (e.g., γ-alumina) and silicacatalysts, and clays including zeolites (e.g., 3-type zeolites, ZSM-5 orY-type zeolites, fluoride-treated β-zeolite catalysts, fluoride-treatedclay catalysts, etc.), sulfonic acid resins (e.g., sulfonated styrenicresins such as Amberlyst® 15), strong acids such as phosphoric acid andsulfuric acid, Lewis acids such boron trifluoride and aluminumtrichloride, and many different types of metal salts including metaloxides (e.g., zirconium oxide or titanium dioxide) and metal chlorides.

Neutral alumina and zeolites can dehydrate alcohols to alkenes butgenerally at higher temperatures and pressures than their acidiccounterparts.

In some embodiments, the dehydration catalyst comprises an acidicalumina, aluminum phosphate, silica-alumina phosphate, amorphoussilica-alumina, aluminosilicate, zirconia, sulfated zirconia, tungstatedzirconia, tungsten carbide, molybdenum carbide, titania, sulfatedcarbon, phosphated carbon, phosphated silica, phosphated alumina, acidicresin, heteropolyacid, inorganic acid, or a combination of any two ormore of the foregoing. In some embodiments, the dehydration catalystfurther comprises a modifier selected from the group consisting of Ce,Y, Sc, La, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, P, B, Bi, and acombination of any two or more of the foregoing. In some embodiments,the dehydration catalyst further comprises an oxide of Ti, Zr, V, Nb,Ta, Mo, Cr, W, Mn, Re, Al, Ga, In, Fe, Co, Ir, Ni, Si, Cu, Zn, Sn, Cd,P, or a combination of any two or more of the foregoing. In someembodiments, the dehydration catalyst further comprises a metal that isCu, Ag, Au, Pt, Ni, Fe, Co, Ru, Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr,Mo, W, Sn, Os, an alloy of any two or more of the foregoing, or acombination of any two or more of the foregoing.

In some embodiments, the dehydration catalyst comprises analuminosilicate zeolite. In some embodiments, the dehydration catalystfurther comprises a modifier that is Ga, In, Zn, Fe, Mo, Ag, Au, Ni, P,Sc, Y, Ta, a lanthanide, or a combination of any two or more of theforegoing. In some embodiments, the dehydration catalyst furthercomprises a metal that is Cu, Ag, Au, Pt, Ni, Fe, Co, Ru, Zn, Cd, Ga,In, Rh, Pd, Ir, Re, Mn, Cr, Mo, W, Sn, Os, an alloy of any two or moreof the foregoing, or a combination of any two or more of the foregoing.

In some embodiments, the dehydration catalyst comprises a bifunctionalpentasil ring-containing aluminosilicate zeolite. In some embodiments,the dehydration catalyst further comprises a modifier that is Ga, In,Zn, Fe, Mo, Ag, Au, Ni, P, Sc, Y, Ta, a lanthanide, or a combination ofany two or more of the foregoing. In some embodiments, the dehydrationcatalyst further comprises a metal that is Cu, Ag, Au, Pt, Ni, Fe, Co,Ru, Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr, Mo, W, Sn, Os, an alloy ofany two or more of the foregoing, or a combination of any two or more ofthe foregoing.

The dehydration reaction is conducted at a temperature and pressurewhere the thermodynamics are favorable. Dehydration reactions can becarried out in both gas and liquid phases with both heterogeneous andhomogeneous catalyst systems in many different reactor configurations.Because water is generated in large quantities in dehydration reactions,dehydration catalysts are used that are generally tolerant to water.Typically, water is removed from the reaction zone with the product.Product alkene(s) either exit the reactor in the gas or liquid phase,depending upon reactor conditions. Water generated by the dehydrationreaction may exit the reactor with unreacted alcohol and alkeneproduct(s) and may be separated by distillation or phase separation.

In some embodiments, the feedstock of a dehydration reaction isrelatively low in water content, as water can inhibit thedehydrogenation reaction. In preferred embodiments, water content in thefeedstock is 50 wt % or less, 30 wt % or less, or 10 wt % or less. If afeedstock of a dehydration reaction comprises greater than 50 wt %water, such as greater than 60 wt %, greater than 70 wt %, greater than80 wt %, or greater that 90 wt % water, a water removal step may be usedprior to the dehydrogenation reaction. For example, a stripper may beused to reduce water content to about 50 wt % or lower.

In some embodiments, a fixed bed reactor is used to facilitateseparation of the catalyst. In some embodiments, a two or three phasefluidized bed or the like is used. In some embodiments, the dehydrationreaction is conducted using a solid catalyst, which is stable to waterproduced during the course of the reaction.

In some embodiments, alkene(s) produced in the dehydration reaction areisolated after the dehydration step, before being used as feedstocks forsubsequent process steps (e.g., dimerization, hydrogenation, etc.).Depending on the particular configuration of the process, isolation ofthe alkenes after formation in the dehydration reactor can offer certainadvantages, for example when the dehydration is carried out in the gasphase, while subsequent process steps are carried out in the liquidphase. However, in some embodiments, alkenes can be used directly fromthe product stream of the dehydration reactor without isolation (e.g.,when the dehydration and the subsequent process steps are carried outunder similar temperature and pressure conditions and/or when suchsubsequent steps are relatively insensitive to water).

Ethylene may be produced by dehydration of ethanol, and propylene may beproduced by dehydration of propanol or isopropanol. However, when1-butanol, 2-butanol, or isobutanol are dehydrated, a mixture of four C4olefins—1-butene, cis-2-butene, trans-2-butene, and isobutene—can beformed. The exact concentration in a product stream of each buteneisomer is determined by the thermodynamics of formation of each isomer.Accordingly, the reaction conditions and catalysts used can bemanipulated to affect the distribution of butene isomers in the productstream. Thus, one can obtain butene mixtures enriched in a particularisomer. As a non-limiting example, isobutanol dehydration reactionconditions (e.g., reactor temperature, pressure, residence time,catalyst identity, etc.) can be adjusted to increase the relativeamounts of 2-butene in a dehydration product stream.

In some embodiments of the various aspects of the invention the alcoholfeedstock of the dehydration reaction comprises a mixture of alcoholsincluding ethanol and isopropanol. This mixture, in turn, can beconverted into a mixture of corresponding olefins by contacting thealcohols with a dehydration catalyst under appropriate conditions. Oncethe alcohol mixture has been converted into a corresponding mixture ofolefins, the resulting olefins can then be separated from one anotherand isolated into product streams, said product streams comprisingpropylene, ethylene or other converted olefins.

Examples of dehydration reactions relevant to this and other aspects ofthe disclosure include:C₂H₅OH→CH₂═CH₂+H₂OC₃H₇OH→CH₃—CH═CH₂+H₂O, andC₄H₉OH→CH₃—CH═CH—CH₃+CH₃—CH₂—CH═CH₂+(etc.)+H₂O

In some embodiments of the various aspects of the disclosure,dehydration reactions are carried out at temperatures of from about 100to 500° C., or of from about 350 to 450° C., or of from about 375 to425° C., or at about 400° C. In some embodiments, dehydration reactionsare carried out at a total internal reactor pressure of from about 0.2to 2 MPa (2 to 20 barg), or of from about 0.2 to 1 MPa (2 to 10 barg),or of from about 0.2 to 0.7 MPa (2 to 7 barg), or at about 0.5 MPa(about 5 barg). In some embodiments, dehydration reactions are carriedout with a whsv, defined as being the ratio of the mass flow rate ofalcohols (e.g., ethanol, isopropanol, or butanol) to the mass ofcatalyst, of from about 1 to 10 h⁻¹, or of from about 2 to 8 h⁻¹, or of0.5 to 2 h⁻¹. In some embodiments, the conversions of alcohols in thedehydration reactions are greater than 90%, or greater than 95%, orgreater than 99%. See, e.g., dehydration of 1-propanol to propene asdisclosed in Lepore et al., 2017, Industrial & Engineering ChemistryResearch 56(15): 4302-4308.

Dimerization

In certain aspects of the methods disclosed herein, ethylene (produced,for example, by dehydration of ethanol) is further reacted in adimerization reactor to produce a stream comprising butene.

Butene may be prepared from ethylene using a homogenous catalyst, forexample, the Alphabutol process (see, e.g., Forestibre et al., 2009, Oil& Gas Sci. and Tech. 6: 649-67), or by using a heterogeneous catalyst asdescribed in Metzger et al., ACS Central Science 2: 148-153, 2016.

The Alphabutol process employs a liquid phase proprietary solublecatalyst system of Ti(IV)/AlEt₃ in the dimerization of ethylene to1-butene at relatively high purity. Ethylene is fed to a continuousliquid phase dimerization reactor. A pump-around system removes theexothermic heat of reaction from the reactor.

The Alphabutol catalyst is the product of a reaction in the reactionmedium between two components: a catalyst precursor mixture containing atitanium-based active metal and a cocatalyst diluted in 1-butene. Thesetwo components are separately and continuously injected into thereaction loop and react in situ to produce the catalyst. The principlecatalytic step involves the coupling of two molecules of ethylene on theactive titanium center to form a titanium (IV) heterocycle which thendecomposes to 1-butene by an intra-molecular 3 hydrogen transfer. Thischemical mechanism explains the high dimer selectivity. The absence ofhydride species ensures low isomerization from 1 to 2-butenes, and lessthan 100 ppm of internal butenes is achieved. When conditions areoptimized, selectivities for 1-butene of around 93% can be attainedusing the Alphabutol process.

In an exemplary Alphabutol process, ethylene dimerization takes place inthe liquid phase at mild conditions (for example, 50-55° C.) and undercontrolled catalyst and ethylene concentrations. The exothermic heat ofreaction is removed by external cooling. No specific solvent is requiredsince the reaction takes place directly in the reactant-productsmixture. The reactor effluent leaves the reaction loop for a spentcatalyst separation system. The spent catalyst is removed andtransformed into a non-toxic material before disposal. The hydrocarbonportion is vaporized and sent to the distillation section. In someembodiments, a first distillation column separates unconverted ethylene,which is recycled to the reaction section; and a second column recovershigh purity 1-butene and a C6+ gasoline cut.

In some embodiments, the feed stream used in the processes hereincomprises at least 10 weight % ethylene. In some embodiments, the feedstream comprises at least 10, 20, 30, 40, 50, 60, 70, 80 or more weight% ethylene. In some embodiments, the feed stream comprises at least 20weight % ethylene. In some embodiments, the feed stream comprises atleast 40 weight % ethylene. In some embodiments, the feed streamcomprises at least 50 weight % ethylene. In some embodiments, the feedstream comprises at least 60 weight % ethylene.

In some embodiments, the dimerization reaction employs a solublecatalyst system of Ti(IV)/AlEt₃. In some embodiments, the dimerizationreaction employs an ionic liquid catalyst comprising at least twocomponents that form a complex. In some embodiments, the ionic liquidcatalyst comprises a first component and a second component. In someembodiments, the first component of the ionic liquid catalyst comprisesa Lewis Acid. In some embodiments, the Lewis acid is a metal halidecompound selected from components such as Lewis Acidic compounds ofGroup 13 metals, including aluminum halides, alkyl aluminum halide,gallium halide, and alkyl gallium halide. In some embodiments, the LewisAcidic compound is a Group 3, 4 or 5 metal halide. Exemplary compoundsinclude ZrCl₄, HfCl₄, NbCl₅, TaCl₅, ScCl₃, YCl₃, and mixtures thereof.

In some embodiments, the second component of the ionic liquid catalystis an organic salt or a mixture of salts. These salts can becharacterized by the general formula Q+A−, wherein Q+ is an ammonium,phosphonium, or sulfonium cation and A− is a negatively charged ion suchas Cl⁻, Br⁻, ClO₄ ⁻, NO₃ ⁻, BF₄ ⁻, BCl₄ ⁻, PF₆ ⁻, SbF₆ ⁻, AlCl₄ ⁻, TaF₆⁻, CuC₂ ⁻, FeCl₃ ⁻, HSO₃ ⁻, RSO₃ ⁻, SO₃CF₃ ⁻, alkyl-aryl sulfonate, andbenzene sulfonate (e.g., 3-sulfurtrioxyphenyl), wherein R is an alkylgroup with 1-12 carbon atoms. In some embodiments, the second componentis selected from those having quaternary ammonium halides containing oneor more alkyl moieties having from about 1 to about 12 carbon atoms,such as, for example, trimethylamine hydrochloride,methyltributylammonium halide, or substituted heterocyclic ammoniumhalide compounds, such as hydrocarbyl substituted pyridinium halidecompounds for example 1-butylpyridinium halide, benzylpyridinium halide,or hydrocarbyl substituted imidazolium halides, such as for example,1-ethyl-3-methyl-imidazolium chloride.

In some embodiments, the ionic liquid catalyst is selected from thegroup consisting of hydrocarbyl substituted pyridinium chloroaluminate,hydrocarbyl substituted imidazolium chloroaluminate, quaternary aminechloroaluminate, trialkyl amine hydrogen chloride chloroaluminate, alkylpyridine hydrogen chloride chloroaluminate, and mixtures thereof. Insome embodiments, the ionic liquid catalyst is an acidic haloaluminateionic liquid, such as an alkyl substituted pyridinium chloroaluminate oran alkyl substituted imidazolium chloroaluminate.

In some embodiments, the liquid catalyst is used in about 5-30 volume %based on the total volume of the reactants. In some embodiments, theionic liquid catalyst is used in about 5-25 volume % based on the totalvolume of the reactants. In some embodiments, the ionic liquid catalystis used in about 5, 10, 15, 20, 25 or 30 volume % based on the totalvolume of the reactants.

In some embodiments, the dimerization catalyst comprises a co-catalystor promoter, which comprises, for example, HCl or organic chloride orhydrogen halides or organic halides wherein halides include Cl, Br, andI ions. In some embodiments, the co-catalyst is anhydrous HCl. Whenorganic chloride is used as the co-catalyst with the ionic liquidcatalyst, HCl may be formed in situ in the reactor during thedimerization process. In some embodiments, co-catalysts or promoters areBronsted acids. A Bronsted acid is any substance that can donate an H⁺ion to a base. Bronsted acids are H⁺-ion or proton donors. Examples ofBronsted acids are HCl, HBr, HI, HF, sulfuric acid, and mixturesthereof. In some embodiments, the co-catalyst enhances the activity ofthe ionic liquid catalyst and improves the yield of the hydrocarbonproduct.

In some embodiments, the ratio of the co-catalyst to ethylene in theolefin feed is adjusted to shift the boiling point distribution of thehydrocarbon product fractions. In some embodiments, the dimerizationconditions include a molar ratio of ethylene to the co-catalyst isbetween about 5 to about 75, between about 10 to about 50, or betweenabout 10 to about 45. In some embodiments, the molar ratio of ethyleneto the co-catalyst is about 10, about 13, about 15, about 20, about 22,about 25, about 30, about 35, about 38, about 40, about 41 or about 45.

Without being bound by any theory, it is believed that the Lewis acidityof the ionic liquid catalyst is enhanced by the Bronsted acidity of theHCl co-catalyst. With the catalyst combination of enhanced Lewis aciditypromoted by a Bronsted acid, the ionic liquid catalyst system is able toactivate ethylene molecules and the dimerization reaction can proceed.The chain length and shifts the carbon number distribution down as wellas the boiling point distribution of the hydrocarbon product.

The dimerization process can be conducted in a semi-batch or continuousmode. Continuous refers to a process that operates (or is intended tooperate) without interruption or cessation. For example, a continuousprocess would be one where the reactants (such as ethylene feed, theionic liquid catalyst and the co-catalyst) are continually introducedinto one or more reactors and the product feed comprising the olefindimers is continually withdrawn. By semi-batch is meant a system thatoperates (or is intended to operate) with periodic interruption. Forexample, a semi-batch process to produce the olefin dimers would be onewhere the reactants are continually introduced into one or more reactorsand the product feed is intermittently withdrawn.

The dimerization reaction can be conducted in any reactor that issuitable for the purpose of dimerization of ethylene in the feedstock inthe presence of an ionic liquid catalyst to obtain a hydrocarbonproduct. Examples of reactors that can be used are continuously stirredtank reactors (CTSR), nozzle reactors (including nozzle loop reactors),tubular reactors (including continuous tubular reactors), fixed bedreactors (including fixed bed contactor reactors), and loop reactors(including static mixer loop reactors).

In some embodiments, the dimerization reaction conditions includetemperatures from about 10° C. to about 149° C., or from about 24° C. toabout 135° C., or from about 38° C. to about 121° C., or from about 50°C. to about 60° C.

In some embodiments, the dimerization reaction is conducted under apressure of about 0.7 MPa-6.9 MPa (7-69 barg), or about 2.4 MPa-4.8 MPa(2.4-4.8 barg), or about 2.7 MPa-3.4 MPa (27-34 barg). In someembodiments, the dimerization reaction is conducted under a pressure ofabout 2.0 MPa-2.7 MPa (20-27 barg). In some embodiments, thedimerization reaction is conducted under a pressure of about 2.7 MPa (28barg), 3.1 MPa (31 barg), 3.2 MPa (32 barg), or 3.4 MPa (34 barg).

Carbonylation

In some embodiments, the methods of the disclosure comprise contacting,in a carbonylation reactor, a carbonylation feed stream comprisingethanol with a catalyst to produce a reactor effluent stream comprisingpropionic acid. In some embodiments, the methods further comprise,before step (a), fermenting, in a bioreactor, a gaseous substrate toproduce the carbonylation feed stream. In some embodiments, the methodsfurther comprise contacting, in a hydrogenation reactor, the firstreactor effluent stream with a catalyst to produce a product streamcomprising propane towards the production of liquefied petroleum gas.

In an exemplary method of carbonylation, a first ethanol-containing feedstream and a second carbon monoxide-containing feed stream are directedto a liquid-phase carbonylation reactor, in which the carbonylationreaction occurs to form propionic acid.

In some embodiments, carbonylation reaction temperatures are from about150 to 250° C. or from about 180 to 225° C. The carbon monoxide partialpressure in the reactor can vary widely but is typically from about 0.2to about 3.0 MPa (about 2 to about 30 bar), such as from about 0.2 toabout 1.0 MPa (about 2 to about 10 bar), or from about 0.2 to about 0.3MPa (about 2 to about 3 bar). See, e.g., kinetics of ethanolcarbonylation in Dake et al., 1984, J. Molecular Catalysis 24: 99-113.

In some embodiments, the carbonylation reactor is a mechanically stirredvessel, a vessel with educted or pump-around mixing, or bubble-columntype vessel, with or without an agitator, within which the reactingliquid or slurry contents are maintained at a predetermined level, andwhich remains substantially constant during normal operation.

The carbonylation catalyst, in some embodiments, is a metal catalystcomprising a Group VIII metal. Suitable Group VIII catalysts includerhodium and/or iridium catalysts. When a rhodium catalyst is used, therhodium catalyst may be added in any suitable form such that rhodium isin the catalyst solution as an equilibrium mixture including[Rh(CO)₂I₂]-anion. Iodide salts optionally maintained in thecarbonylation reaction mixtures of the processes described herein may bein the form of a soluble salt of an alkali metal or alkaline earthmetal, quaternary ammonium, phosphonium salt, or mixtures thereof. Insome embodiments, the catalyst co-promoter is lithium iodide, lithiumacetate, or mixtures thereof. The salt co-promoter may be added as anon-iodide salt that will generate an iodide salt. The iodide catalyststabilizer may be introduced directly into the reaction system.Alternatively, the iodide salt may be generated in-situ since under theoperating conditions of the reaction system, a wide range of non-iodidesalt precursors will react with methyl iodide or hydroiodic acid in thereaction medium to generate the corresponding co-promoter iodide saltstabilizer. For additional detail regarding rhodium catalysis and iodidesalt generation, see U.S. Pat. Nos. 5,001,259; 5,026,908; 5,144,068 and7,005,541.

In some embodiments, the halogen-containing catalyst promoter of thecarbonylation catalyst system comprises a halogen compound comprising anorganic halide. Thus, alkyl, aryl, and substituted alkyl or aryl halidescan be used. In some embodiments, the halogen-containing catalystpromoter is present in the form of an alkyl halide. In some embodiments,the halogen-containing catalyst promoter is present in the form of analkyl halide in which the alkyl radical corresponds to the alkyl radicalof the feed alcohol, which is being carbonylated. Thus, in thecarbonylation of ethanol to propionic acid, the halide promoter maycomprise ethyl halide, and such as ethyl iodide.

The components of the reaction medium are maintained within definedlimits to ensure sufficient production of priopionic acid. The reactionmedium contains a concentration of the metal catalyst, e.g. rhodiumcatalyst, in an amount from 100 to 3000 wppm, e.g., from 400 to 2000wppm, or from 400 to 1500 wppm as rhodium. The concentration of water inthe reaction medium is maintained to be less than 14 weight %, e.g.,from 0.1 weight % to 14 weight %, from 0.2 weight % to 10 weight % orfrom 0.25 weight % to 5 weight %. Preferably, the reaction is conductedunder low water conditions and the reaction medium contains less than 4weight % water, e.g., less than 3.5 weight %, less than 3 weight %, orless than 2 weight %. In terms of ranges, the reaction medium contains0.1 to 3.5 weight % water, e.g, from 0.1 to 3 weight % or from 0.5 to2.8 weight %. The concentration of ethyl iodide in the reaction mediumis maintained to be from 1 to 25 weight %, e.g., from 5 to 20 weight %,from 4 to 13.9 weight %. The concentration of iodide salt, e.g., lithiumiodide, in the reaction medium is maintained to be from 1 to 25 weight%, e.g., from 2 to 20 weight %, from 3 to 20 weight %. The concentrationof ethyl acetate in the reaction medium is maintained to be from 0.5 to30 weight %, e.g., from 0.3 to 20 weight %, from 0.6 to 4.1 weight %.The foregoing amounts are based on the total weight of the reactionmedium. The ranges disclosed in this application include the endpoints,subranges and individual values.

The concentration of propionic acid in the reaction medium is generallymore than 30 weight %, e.g. more than 40 weight % or more than 50 weight%.

In some embodiments, the reaction rates are obtained even at low waterconcentrations by maintaining in the reaction medium an ester of thedesired carboxylic acid and an alcohol, such as the alcohol used in thecarbonylation, and an additional iodide ion that is over and above theiodide ion that is present as hydrogen iodide. In some embodiments, theester is ethyl acetate. The additional iodide ion is in some embodimentsan iodide salt, with lithium iodide (LiI) being used in certainembodiments. It has been found, as described in U.S. Pat. No. 5,001,259,that under low water concentrations, ethyl acetate and lithium iodideact as rate promoters only when relatively high concentrations of eachof these components are present and that the promotion is higher whenboth of these components are present simultaneously.

The carbonylation reaction of ethanol to propionic acid product may becarried out by contacting the ethanol feed with gaseous carbon monoxidebubbled through an solvent reaction medium containing the rhodiumcatalyst, ethyl iodide (EtI) promoter, ethyl acetate (EtAc), andadditional soluble iodide salt, at conditions of temperature andpressure suitable to form the carbonylation product. It will begenerally recognized that it is the concentration of iodide ion in thecatalyst system that is important and not the cation associated with theiodide, and that at a given molar concentration of iodide the nature ofthe cation is not as significant as the effect of the iodideconcentration. Any metal iodide salt, or any iodide salt of any organiccation, or other cations such as those based on amine or phosphinecompounds (optionally quaternary cations), can be maintained in thereaction medium provided that the salt is sufficiently soluble in thereaction medium to provide the desired level of the iodide. When theiodide is a metal salt, preferably it is an iodide salt of a member ofthe group consisting of the metals of groups 1 and 2 of the IUPACperiodic table. In particular, alkali metal iodides are useful, withlithium iodide being particularly suitable.

In a low water carbonylation process, the additional iodide ion over andabove the iodide ion present as hydrogen iodide is generally present inthe catalyst solution in amounts such that the total iodide ionconcentration is from 1 to 25 weight % and the ethyl acetate isgenerally present in amounts from 0.5 to 30 weight %, and the ethyliodide is generally present in amounts from 1 to 25 weight %. Therhodium catalyst is generally present in amounts from 200 to 3000 wppm.

Hydrogenation

In each of the disclosed aspects, the methods described herein comprisehydrogenation of a C3-C4 olefin or propionic acid with a catalyst toproduce a product stream comprising propane and/or butane (i.e., aliquefied petroleum gas product stream).

The olefin (i.e., propylene and/or butene) hydrogenation(s) may beperformed using well-known and/or readily available commercialhydrogenation catalyst(s) at only slightly elevated temperatures andpressures (i.e., relatively mild reaction conditions). The reaction canbe carried out at any suitable pressure, such as in the range of fromabout 0.7 to about 8.2 MPa (about 7 to about 82 barg), or from about 0.7to 2.0 MPa, or from about 1.0 to 2.0 MPa. In some embodiments, thereaction is carried out above 1.7 MPa (about 17 barg) to maximize thehydrogenation rate.

The olefin hydrogenation reaction can be carried out at any suitabletemperature with favorable equilibria for the saturation reaction,generally less than about 400° C. In some embodiments, the hydrogenationreaction is carried out at a temperature of less than 250° C.

For hydrogenation of C3-C4 olefins (see, e.g., U.S. Pat. No. 4,482,767),common hydrogenation catalysts include insoluble metals such aspalladium (such as in the form Pd—C), platinum, nickel (such as in theform Raney-Ni or nickel-alumina), cobalt, or a mixture of these metals.Other non-limiting examples of catalysts for hydrogenation of olefinsinclude Ni-0750 E (BASF), nickel supported on kieselguhr, CriterionKL6565, or JM 10R39.

In some embodiments, olefin hydrogenation is carried out in aliquid-phase, vapor-phase, and/or trickle bed reactor. In someembodiments, olefin hydrogenation is carried out in a trickle bed or invapor phase. In some embodiments, the olefin-containing process streamis passed downward through a fixed bed of the hydrogenation catalyst asa vapor phase stream.

Following passage through the olefin hydrogenation zone, in someembodiments, a following step is separation of any remaining hydrogenand unreacted olefin from the product LPG and recycling the reagentsback to the hydrogenation reaction.

In some embodiments, olefin hydrogenation is carried out in the presenceof hydrogen equal to about 110 to about 130 mole percent of thestoichiometrically required amount of hydrogen. In some embodiments,hydrogen present in the feed gas stream is sufficient. In someembodiments, additional hydrogen is passed into the hydrogenationreactor. In other embodiments, no additional hydrogen is passed into thehydrogenation reactor in order to maximize utilization of feed gashydrogen. In embodiments where additional hydrogen is passed into thehydrogenation reactor, the hydrogen or electricity used to produce thehydrogen is preferably acquired from renewable resources such as wind,solar, geothermal, or biomass.

In some aspects of the disclosure, propionic acid is hydrogenated toproduce propane and water which can be easily separated by fractionationor by condensing the water. Hydrogenation of carboxylic acids, such aspropionic acid, to alkanes, such as propane, can be performed using, forexample, bimetallic catalysts, such as a catalyst of rhenium-palladiumsupported on graphite (a Pd/Re/C catalyst) (see, e.g., Ullrich andBreit, 2018, ACS Catal. 8: 785-89).

In some embodiments, the carboxylic acid (e.g., propionic acid)hydrogenation reaction produces both the corresponding alcohol (e.g.,propanol) and the corresponding alkane (e.g., propane), with the alcoholbeing the primary product in early stages of the reaction, but withhydrogenation of alcohol to furnish alkane proceeding in later stages ofthe reaction, particularly once the starting carboxylic acid material isconsumed. In some embodiments, higher temperatures and/or pressures leadto increased selectivity of the alkane product versus the alcoholproduct. Thus, in some embodiments, hydrogenation of carboxylic acid toalkane is performed at a reaction temperature of about 130° C. to about200° C., or about 140° C. to about 190° C., or about 150° C. to about180° C., or about 150° C. to about 170° C. In some embodiments, thecarboxylic acid hydrogenation reaction is performed at a temperature ofabout 130° C., or 140° C., or 150° C., or 160° C., or 170° C., or 180°C., or 190° C., or 200° C. In some embodiments, the carboxylic acidhydrogenation reaction is performed at a temperature of about 160° C. Insome embodiments, the hydrogenation of carboxylic acid to alkane isperformed at a reaction pressure of about 2.0 MPa to 4.0 MPa, or about2.5 MPa to about 3.5 MPa, or about 2.7 to about 3.3 MPa, or about 2.0MPa, or 2.2 MPa, or 2.4 MPa, or 2.5 MPa, or 2.6 MPa, or 2.7 MPa, or 2.8MPa, or 2.9 MPa, or 3.0 MPa, or 3.1 MPa, or 3.2 MPa, or 3.3 MPa, or 3.4MPa, or 3.5 MPa, or 3.6 MPa, or 3.8 MPa, or 4.0 MPa. In someembodiments, the carboxylic acid hydrogenation reaction is performed ata pressure of about 3.0 MPa.

The effluent stream of the hydrogenation zone is preferably passedthrough an indirect heat exchanger in which it is cooled sufficiently toeffect a partial condensation of the hydrocarbons present in thisstream. Such light gases as hydrogen, nitrogen, methane, and carbondioxide are not condensed at this point. Essentially all of thesaturated alkane (i.e., propane and/or butane) is preferably condensed.The condensed propane/butane is removed as an LPG stream having a lowolefin content. Such low olefin contents are desirable in an LPG streamas evidenced by the fact that the olefin content is one of the qualityindicators of LPG. The product LPG may be combined with other streams ormay be sold or used as produced.

Fermentation

Alcohols, such as ethanol, C3 alcohols, and C4 alcohols, used to produceLPG are preferably produced by gas fermentation. For instance,microorganisms relevant to fermentation aspects of the disclosure mayproduce or may be engineered to produce ethanol (US 2009/0203100),isopropanol (US 2013/0224838), butanol (US 2010/0105115 and US2011/0236941), and 2-butanol (US 2013/0330809.

The term “fermentation” should be interpreted as a metabolic processthat produces chemical changes in a substrate. For example, afermentation process receives one or more substrates and produces one ormore products through utilization of one or more microorganisms. Theterm “fermentation,” “gas fermentation” and the like should beinterpreted as the process which receives one or more substrate, such assyngas produced by gasification and produces one or more product throughthe utilization of one or more C1-fixing microorganism. Preferably thefermentation process includes the use of one or more bioreactor. Thefermentation process may be described as either “batch” or “continuous.”“Batch fermentation” is used to describe a fermentation process wherethe bioreactor is filled with raw material, e.g. the carbon source,along with microorganisms, where the products remain in the bioreactoruntil fermentation is completed. In a “batch” process, afterfermentation is completed, the products are extracted, and thebioreactor is cleaned before the next “batch” is started. “Continuousfermentation” is used to describe a fermentation process where thefermentation process is extended for longer periods of time, and productand/or metabolite is extracted during fermentation. Preferably thefermentation process is continuous.

A “microorganism” is a microscopic organism, especially a bacterium,archea, virus, or fungus. Microorganisms relevant to fermentationaspects of the disclosure are typically bacteria. As used herein,recitation of “microorganism” should be taken to encompass “bacterium.”

Microorganisms relevant to fermentation aspects of the disclosure may beclassified based on functional characteristics. For example,microorganisms relevant to fermentation aspects of the disclosure may beor may be derived from a C1-fixing microorganism, an anaerobe, anacetogen, an ethanologen, a carboxydotroph, and/or a methanotroph. Table1 provides a representative list of microorganisms and identifies theirfunctional characteristics.

TABLE 1 Wood- C1- Ljungdahl fixing Anaerobe Acetogen EthanologenAutotroph Carboxydotroph Acetobacterium woodii + + + + +/− ¹ + −Alkalibaculum bacchii + + + + + + + Blautia producta + + + + − + +Butyribacterium + + + + + + + methylotrophicum Clostridiumaceticum + + + + − + + Clostridium + + + + + + + autoethanogenumClostridium + + + + + + + carboxidivorans Clostridiumcoskatii + + + + + + + Clostridium drakei + + + + − + +Clostridium + + + + − + + formicoaceticum Clostridium + + + + + + +ljungdahlii Clostridium magnum + + + + − + +/− ² Clostridiumragsdalei + + + + + + + Clostridium scatologenes + + + + − + +Eubacterium limosum + + + + − + + Moorella + + + + + + +thermautotrophica Moorella thermoacetica + + + + − ³ + + (formerlyClostridium thermoaceticum) Oxobacter pfennigii + + + + − + + Sporomusaovata + + + + − + +/− ⁴ Sporomusa silvacetica + + + + − + +/− ⁵Sporomusa sphaeroides + + + + − + +/− ⁶ Thermoanaerobacter + + + + − + −kiuvi ¹ Acetobacterium woodi can produce ethanol from fructose, but notfrom gas. ² It has not been investigated whether Clostridium magnum cangrow on CO. ³ One strain of Moorella thermoacetica, Moorella sp.HUC22-1, has been reported to produce ethanol from gas. ⁴ It has notbeen investigated whether Sporomusa ovata can grow on CO. ⁵ It has notbeen investigated whether Sporomusa silvacetica can grow on CO. ⁶ It hasnot been investigated whether Sporomusa sphaeroides can grow on CO.

“Wood-Ljungdahl” refers to the Wood-Ljungdahl pathway of carbon fixationas described, e.g., by Ragsdale, Biochim Biophys Acta, 1784: 1873-1898,2008. “Wood-Ljungdahl microorganisms” refers, predictably, tomicroorganisms containing the Wood-Ljungdahl pathway. Generally,microorganisms relevant to fermentation aspects of the disclosurecontain a native Wood-Ljungdahl pathway. Herein, a Wood-Ljungdahlpathway may be a native, unmodified Wood-Ljungdahl pathway or it may bea Wood-Ljungdahl pathway with some degree of genetic modification (e.g.,overexpression, heterologous expression, knockout, etc.) so long as itstill functions to convert CO, CO₂, and/or H₂ to acetyl-CoA.

“C1” refers to a one-carbon molecule, for example, CO, CO₂, CH₄, orCH₃OH. “C1-oxygenate” refers to a one-carbon molecule that alsocomprises at least one oxygen atom, for example, CO, CO₂, or CH₃OH.“C1-carbon source” refers a one carbon-molecule that serves as a partialor sole carbon source for microorganisms relevant to fermentationaspects of the disclosure. For example, a C1-carbon source may compriseone or more of CO, CO₂, CH₄, CH₃OH, or CH₂O₂. Preferably, the C1-carbonsource comprises one or both of CO and CO₂. A “C1-fixing microorganism”is a microorganism that has the ability to produce one or more productsfrom a C1 carbon source. Typically, microorganisms relevant tofermentation aspects of the disclosure are C1-fixing bacteria. In someembodiments, microorganisms relevant to fermentation aspects of thedisclosure are derived from C1-fixing microorganisms identified in Table1.

An “anaerobe” is a microorganism that does not require oxygen forgrowth. An anaerobe may react negatively or even die if oxygen ispresent above a certain threshold. However, some anaerobes are capableof tolerating low levels of oxygen (e.g., 0.000001-5% oxygen).Typically, microorganisms relevant to fermentation aspects of thedisclosure are anaerobes. In some embodiments, microorganisms relevantto fermentation aspects of the disclosure are derived from anaerobes asidentified in Table 1.

“Acetogens” are obligately anaerobic bacteria that use theWood-Ljungdahl pathway as their main mechanism for energy conservationand for synthesis of acetyl-CoA and acetyl-CoA-derived products, such asacetate (Ragsdale, Biochim Biophys Acta, 1784: 1873-1898, 2008). Inparticular, acetogens use the Wood-Ljungdahl pathway as a (1) mechanismfor the reductive synthesis of acetyl-CoA from CO₂, (2) terminalelectron-accepting, energy conserving process, (3) mechanism for thefixation (assimilation) of CO₂ in the synthesis of cell carbon (Drake,Acetogenic Prokaryotes, In: The Prokaryotes, 3rd edition, p. 354, NewYork, N.Y., 2006). All naturally occurring acetogens are C1-fixing,anaerobic, autotrophic, and non-methanotrophic. Typically,microorganisms relevant to fermentation aspects of the disclosure areacetogens. In some embodiments, microorganisms relevant to fermentationaspects of the disclosure are derived from acetogens as identified inTable 1.

An “ethanologen” is a microorganism that produces or is capable ofproducing ethanol. Typically, microorganisms relevant to fermentationaspects of the disclosure are ethanologens. In some embodiments,microorganisms relevant to fermentation aspects of the disclosure arederived from ethanologens as identified in Table 1.

An “autotroph” is a microorganism capable of growing in the absence oforganic carbon. Instead, autotrophs use inorganic carbon sources, suchas CO and/or CO₂. Typically, microorganisms relevant to fermentationaspects of the disclosure are autotrophs. In some embodiments,microorganisms relevant to fermentation aspects of the disclosure arederived from autotrophs as identified in Table 1.

A “carboxydotroph” is a microorganism capable of utilizing CO as a solesource of carbon and energy. Typically, microorganisms relevant tofermentation aspects of the disclosure are carboxydotrophs. In someembodiments, microorganisms relevant to fermentation aspects of thedisclosure are derived from carboxydotrophs as identified in Table 1.

A “methanotroph” is a microorganism capable of utilizing methane as asole source of carbon and energy. In some embodiments, microorganismsrelevant to fermentation aspects of the disclosure are methanotrophs orare derived from methanotrophs. In other embodiments, microorganismsrelevant to fermentation aspects of the disclosure are not methanotrophsor are not derived from methanotrophs.

More broadly, microorganisms relevant to fermentation aspects of thedisclosure may be derived from any genus or species identified inTable 1. For example, the microorganism may be a member of a genusselected from the group consisting of Acetobacterium, Alkalibaculum,Blautia, Butyribacterium, Clostridium, Eubacterium, Moorella, Oxobacter,Sporomusa, and Thermoanaerobacter. In particular, the microorganism maybe derived from a parental bacterium selected from the group consistingof Acetobacterium woodii, Alkalibaculum bacchii, Blautia producta,Butyribacterium methylotrophicum, Clostridium aceticum, Clostridiumautoethanogenum, Clostridium carboxidivorans, Clostridium coskatii,Clostridium drakei, Clostridium formicoaceticum, Clostridiumljungdahlii, Clostridium magnum, Clostridium ragsdalei, Clostridiumscatologenes, Eubacterium limosum, Moorella thermautotrophica, Moorellathermoacetica, Oxobacter pfennigii, Sporomusa ovata, Sporomusasilvacetica, Sporomusa sphaeroides, and Thermoanaerobacter kiuvi.

In some embodiments, microorganisms relevant to fermentation aspects ofthe disclosure are derived from the cluster of Clostridia comprising thespecies Clostridium autoethanogenum, Clostridium ljungdahlii, andClostridium ragsdalei. These species were first reported andcharacterized by Abrini, Arch Microbiol, 161: 345-351, 1994 (Clostridiumautoethanogenum), Tanner, Int J System Bacteriol, 43: 232-236, 1993(Clostridium ljungdahlii), and Huhnke, WO 2008/028055 (Clostridiumragsdalei). Isolates and mutants of Clostridium autoethanogenum includeJAI-1 (DSM10061) (Abrini, Arch Microbiol, 161: 345-351, 1994), LBS1560(DSM19630) (WO 2009/064200), and LZ1561 (DSM23693) (WO 2012/015317).Isolates and mutants of Clostridium ljungdahlii include ATCC 49587(Tanner, Int J Syst Bacteriol, 43: 232-236, 1993), PETCT (DSM13528, ATCC55383), ERI-2 (ATCC 55380) (U.S. Pat. No. 5,593,886), C-01 (ATCC 55988)(U.S. Pat. No. 6,368,819), 0-52 (ATCC 55989) (U.S. Pat. No. 6,368,819),and OTA-1 (Tirado-Acevedo, Production of bioethanol from synthesis gasusing Clostridium ljungdahlii, PhD thesis, North Carolina StateUniversity, 2010). Isolates and mutants of Clostridium ragsdalei includePI 1 (ATCC BAA-622, ATCC PTA-7826) (WO 2008/028055).

Metabolic engineering of microorganisms, such as Clostridia, cantremendously expand their ability to produce many important chemicalmolecules. However, until recently, Clostridia were consideredgenetically intractable and therefore generally off limits to extensivemetabolic engineering efforts. In recent years several different methodsfor genome engineering for Clostridia have been developed includingintron-based methods (ClosTron) (Kuehne, Strain Eng: Methods andProtocols, 389-407, 2011), allelic exchange methods (ACE) (Heap, NuclAcids Res, 40: e59, 2012; Ng, PLoS One, 8: e56051, 2013), Triple Cross(Liew, Frontiers Microbiol, 7: 694, 2016), methods mediated throughI-Scel (Zhang, Journal Microbiol Methods, 108: 49-60, 2015), MazF(Al-Hinai, Appl Environ Microbiol, 78: 8112-8121, 2012), or others(Argyros, Appl Environ Microbiol, 77: 8288-8294, 2011), Cre-Lox (Ueki,mBio, 5: e01636-01614, 2014), and CRISPR/Cas9 (Nagaraju, BiotechnolBiofuels, 9: 219, 2016). However, it remains extremely challenging toiteratively introduce more than a few genetic changes, due to slow andlaborious cycling times and limitations on the transferability of thesegenetic techniques across species. Furthermore, C1 metabolism inClostridia is not yet sufficiently well-understood to reliably predictmodifications that will maximize C1 uptake, conversion, andcarbon/energy/redox flows towards product synthesis. Accordingly,introduction of target pathways in Clostridia remains a tedious andtime-consuming process.

“Gaseous substrate” and “substrate” refer to a carbon and/or energysource for microorganisms relevant to fermentation aspects of thedisclosure. Typically, the substrate is gaseous and comprises aC1-carbon source, for example, CO, CO₂, and/or CH₄. Preferably, thesubstrate comprises a C1-carbon source of CO or CO+CO₂. The substratemay further comprise other non-carbon components, such as H₂, N₂, orelectrons.

The substrate for the microbial fermentation step generally comprises atleast some amount of CO, such as about 1, 2, 5, 10, 20, 30, 40, 50, 60,70, 80, 90, or 100 mol % CO. The substrate may comprise a range of CO,such as about 20-80, 30-70, or 40-60 mol % CO. Preferably, the substratecomprises about 40-70 mol % CO (e.g., steel mill or blast furnace gas),about 20-30 mol % CO (e.g., basic oxygen furnace gas), or about 15-45mol % CO (e.g., syngas). In some embodiments, the substrate may comprisea relatively low amount of CO, such as about 1-10 or 1-20 mol % CO.Microorganisms relevant to fermentation aspects of the disclosuretypically convert at least a portion of the CO in the substrate to aproduct. In some embodiments, the substrate comprises no orsubstantially no (<1 mol %) CO.

The substrate may comprise some amount of H₂. For example, the substratemay comprise about 1, 2, 5, 10, 15, 20, or 30 mol % H₂. In someembodiments, the substrate may comprise a relatively high amount of H₂,such as about 60, 70, 80, or 90 mol % H₂. In further embodiments, thesubstrate comprises no or substantially no (<1 mol %) H₂.

The substrate may comprise some amount of CO₂. For example, thesubstrate may comprise about 1-80 or 1-30 mol % CO₂. In someembodiments, the substrate may comprise less than about 20, 15, 10, or 5mol % CO₂. In some embodiments, the substrate comprises no orsubstantially no (<1 mol %) CO₂.

Although the substrate is typically gaseous, the substrate may also beprovided in alternative forms. For example, the substrate may bedissolved in a liquid saturated with a CO-containing gas using amicrobubble dispersion generator. By way of further example, thesubstrate may be adsorbed onto a solid support.

The substrate and/or C1-carbon source may be a waste gas obtained as abyproduct of an industrial process or from some other source, such asfrom automobile exhaust fumes or biomass gasification. In someembodiments, the industrial process is selected from the groupconsisting of ferrous metal products manufacturing, such as a steel millmanufacturing, non-ferrous products manufacturing, petroleum refining,coal gasification, electric power production, carbon black production,ammonia production, methanol production, and coke manufacturing. Inthese embodiments, the substrate and/or C1-carbon source may be capturedfrom the industrial process before it is emitted into the atmosphere,using any convenient method.

The substrate and/or C1-carbon source may be syngas, such as syngasobtained by gasification of coal or refinery residues, gasification ofbiomass or lignocellulosic material, or reforming of natural gas. Insome embodiments, the syngas may be obtained from the gasification ofmunicipal solid waste or industrial solid waste.

Syngas composition can be improved to provide a desired or optimumH₂:CO:CO₂ ratio. The syngas composition may be improved by adjusting thefeedstock being fed to the gasification process. The desired H₂:CO:CO₂ratio is dependent on the desired fermentation product of thefermentation process. For ethanol, the optimum H₂:CO:CO₂ ratio would be:

${(x)\text{:}(y)\text{:}\left( \frac{x - {2\; y}}{3} \right)},$where x>2y, in order to satisfy the stoichiometry for ethanol production

$\left. {{(x)H_{2}} + {(y){CO}} + {\left( \frac{x - {2y}}{3} \right){CO}_{2}}}\rightarrow{{\left( \frac{x + y}{6} \right)C_{2}H_{5}{OH}} + {\left( \frac{x - y}{2} \right)H_{2}{O.}}} \right.$

Operating the fermentation process in the presence of hydrogen has theadded benefit of reducing the amount of CO₂ produced by the fermentationprocess. For example, a gaseous substrate comprising minimal H₂ willtypically produce ethanol and CO₂ by the following stoichiometry[6CO+3H₂O→C₂H₅OH+4CO₂]. As the amount of hydrogen utilized by theC1-fixing bacterium increases, the amount of CO₂ produced decreases[e.g., 2CO+4H₂→C₂H₅OH+H₂O].

When CO is the sole carbon and energy source for ethanol production, aportion of the carbon is lost to CO₂ as follows:6CO+3H₂O→C₂H₅OH+4CO₂ (ΔG°=−224.90 kJ/mol ethanol)

As the amount of H₂ available in the substrate increases, the amount ofCO₂ produced decreases. At a stoichiometric ratio of 2:1 (H₂:CO), CO₂production is completely avoided.5CO+1H₂+2H₂O→1C₂H₅OH+3CO₂(ΔG°=−204.80 kJ/mol ethanol)4CO+2H₂+1H₂O→1C₂H₅OH+2CO₂ (ΔG°=−184.70 kJ/mol ethanol)CO+3H₂→1C₂H₅OH+1CO₂ (ΔG°=−164.60 kJ/mol ethanol)

The composition of a gaseous substrate may have a significant impact onthe efficiency and/or cost of a reaction. In some embodiments, a gaseoussubstrate may comprise a contaminant, such as a contaminant thatdecreases the rate of, or prevents, a chemical reaction. The contaminantmay inhibit a microorganism or the activity of a catalyst. Contaminantsinclude, but are not limited to, sulphur compounds, aromatic compounds,alkynes, alkenes, alkanes, olefins, nitrogen compounds,phosphorous-containing compounds, particulate matter, solids, oxygen,halogenated compounds, silicon-containing compounds, carbonyls, metals,alcohols, esters, ketones, peroxides, aldehydes, ethers, and tars. Inparticular embodiments, contaminants include hydrogen cyanide (HCN),acetylene (C₂H₂), BTEX (benzene, toluene, ethylbenzene, xylene),hydrogen sulfide (H₂S), and carbonyl sulfide (COS). The presence ofoxygen may reduce the efficiency of an anaerobic fermentation process.Depending on the composition of the substrate, it may be desirable totreat, scrub, or filter the gaseous substrate to remove any undesiredcontaminants and/or increase the concentration of desirable components.

Typically, the fermentation is performed in a bioreactor. The term“bioreactor” includes a fermentation device consisting of one or morevessels, towers, or piping arrangements, such as a continuous stirredtank reactor (CSTR), immobilized cell reactor (ICR), trickle bed reactor(TBR), bubble column, gas lift fermenter, static mixer, or other vesselor other device suitable for gas-liquid contact. In some embodiments,the bioreactor may comprise a first growth reactor and a secondfermentation reactor. The substrate may be provided to one or both ofthese reactors.

The culture is generally maintained in an aqueous culture medium thatcontains nutrients, vitamins, and/or minerals sufficient to permitgrowth of the microorganism. Preferably the aqueous culture medium is ananaerobic microbial growth medium, such as a minimal anaerobic microbialgrowth medium. Suitable media are well known in the art.

The fermentation should desirably be carried out under appropriateconditions for production of the target product. Reaction conditions toconsider include pressure (or partial pressure), temperature, gas flowrate, liquid flow rate, media pH, media redox potential, agitation rate(if using a continuous stirred tank reactor), inoculum level, maximumgas substrate concentrations to ensure that gas in the liquid phase doesnot become limiting, and maximum product concentrations to avoid productinhibition. In particular, the rate of introduction of the substrate maybe controlled to ensure that the concentration of gas in the liquidphase does not become limiting, since products may be consumed by theculture under gas-limited conditions.

Target products may be separated or purified from a fermentation brothusing any method or combination of methods known in the art, including,for example, fractional distillation, evaporation, pervaporation, gasstripping, phase separation, and extractive fermentation, including forexample, liquid-liquid extraction. In some embodiments, target productsare recovered from the fermentation broth by continuously removing aportion of the broth from the bioreactor, separating microbial cellsfrom the broth (conveniently by filtration), and recovering one or moretarget products from the broth. Alcohols may be recovered, for example,by distillation.

While the disclosure has been described in terms of various embodiments,it is understood that variations and modifications will occur to thoseskilled in the art. Therefore, it is intended that the appended claimscover all such equivalent variations that come within the scope of thedisclosure as claimed. In addition, the section headings used herein arefor organizational purposes only and are not to be construed as limitingthe subject matter described.

Each embodiment herein described may be combined with any otherembodiment or embodiments unless clearly indicated to the contrary. Inparticular, any feature or embodiment indicated as being preferred oradvantageous may be combined with any other feature or features orembodiment or embodiments indicated as being preferred or advantageous,unless clearly indicated to the contrary.

EMBODIMENTS

A first embodiment is a method of producing liquefied petroleum gascomprising contacting a feed stream comprising a C3 alcohol and/or a C4alcohol with one or more catalysts to produce a product streamcomprising propane and/or butane wherein the feed stream is a product ofmicrobial fermentation of a gaseous substrate. Another embodiment is thefirst embodiment wherein the C3 alcohol comprises isopropanol and/or1-propanol; and the C4 alcohol comprises butanol or an isomer ofbutanol. Another embodiment is the first Embodiment wherein the one ormore catalysts comprise a dehydration catalyst and/or a hydrogenationcatalyst. Another embodiment is any of the above embodiments wherein thedehydration catalyst is selected from acidic alumina, aluminumphosphate, silica-alumina phosphate, amorphous silica-alumina,aluminosilicate, zirconia, sulfated zirconia, tungstated zirconia,tungsten carbide, molybdenum carbide, titania, sulfated carbon,phosphated carbon, phosphated silica, phosphated alumina, acidic resin,heteropolyacid, inorganic acid, and any combination thereof. Anotherembodiment is wherein the hydrogenation catalyst comprises a Ni-alumina,Pd—C, Raney-Ni, Co, or Pt catalyst, or any combination thereof. Anotherembodiment is wherein a dehydration reactor comprises the dehydrationcatalyst and a hydrogenation reactor comprises the hydrogenationcatalyst. Another embodiment is wherein the catalyst comprisesfunctionality of a dehydration catalyst and functionality of ahydrogenation catalyst. Another embodiment is any of the previousembodiments comprising contacting, in the dehydration reactor, the feedstream comprising the C3 alcohol and/or the C4 alcohol with thedehydration catalyst to produce an effluent stream comprising the C3alkene and/or the C4 alkene; and contacting, in the hydrogenationreactor, the effluent stream comprising the C3 alkene and/or the C4alkene with hydrogen and the hydrogenation catalyst to produce theproduct stream comprising the propane and/or butane. Another embodimentis any of the previous embodiments wherein the C3 alkene comprisespropene; and the C4 alkene comprises butene, an isomer of butene, and/orbutadiene. Another embodiment is wherein the dehydration reactoroperates at a temperature of from 100° C. to 500° C., of from 350° C. to450° C., or of from 375° C. to about 425° C. Another embodiment iswherein the dehydration reactor operates at a pressure of from 0.2 MPato 2 MPa, of from 0.2 MPa to 1 MPa, or of from 0.2 MPa to 0.7 MPa.Another embodiment is wherein the dehydration reactor operates at aweight hourly space velocity (whsv) of from 1 h⁻¹ to 10 h⁻¹, of from 2h⁻¹ to 8 h⁻¹, or of from 0.5 h⁻¹ to 2 h⁻¹. Another embodiment is whereinthe hydrogenation reactor operates at a temperature of less than 400°C., of less than 250° C., or of 100° C. to 150° C. Another embodiment iswherein the hydrogenation reactor operates at a pressure above 1.7 MPa,of 0.7 MPa to 8.2 MPa, of 0.7 MPa to 2.0 MPa, or of 1.0 MPa to 2.0 MPa.

A second embodiment is a method of producing liquefied petroleum gascomprising contacting, in a dehydration reactor, a dehydration feedstream comprising ethanol with a dehydration catalyst to produce a firstreactor effluent stream comprising ethylene; wherein the dehydrationfeed stream is a product of microbial fermentation of a gaseoussubstrate; contacting, in a dimerization reactor, the first reactoreffluent stream with a dimerization catalyst to produce a second reactoreffluent stream comprising butene; and contacting, in a hydrogenationreactor, the second reactor effluent stream and hydrogen with ahydrogenation catalyst to produce a product stream comprising butane.Another embodiment is the second embodiment wherein the dehydrationreactor operates at a temperature of from 100° C. to 500° C., of from350° C. to 450° C., or of from 375° C. to 425° C. Another embodiment isthe second embodiment wherein the dehydration reactor operates at apressure of from 0.2 MPa to 2 MPa, of from 0.2 MPa to 1 MPa, or of from0.2 MPa to 0.7 MPa. Another embodiment is the second embodiment whereinthe dehydration reactor operates at a whsv of from 1 h⁻¹ to 10 h⁻¹, offrom 2 h⁻¹ to 8 h⁻¹, or of 0.5 h⁻¹ to 2 h⁻¹. Another embodiment is thesecond embodiment wherein the dehydration catalyst is selected fromacidic alumina, aluminum phosphate, silica-alumina phosphate, amorphoussilica-alumina, aluminosilicate, zirconia, sulfated zirconia, tungstatedzirconia, tungsten carbide, molybdenum carbide, titania, sulfatedcarbon, phosphated carbon, phosphated silica, phosphated alumina, acidicresin, heteropolyacid, inorganic acid, and any combination thereof.Another embodiment is the second embodiment wherein the dimerizationreactor operates at a temperature of from 10° C. to 150° C., of from 24°C. to 135° C., of from 38° C. to 121° C., or of from 50° C. to 60° C.Another embodiment is the second embodiment wherein the dimerizationreactor operates at a pressure of 0.7 MPa to 6.9 MPa, of 2.4 MPa to 4.8MPa, of 2.8 MPa to 3.4 MPa, or of 2.0 MPa to 2.7 MPa. Another embodimentis the second embodiment wherein the dimerization catalyst comprises anionic liquid catalyst. Another embodiment is the second embodimentwherein the dimerization catalyst comprises a co-catalyst or a promoter.Another embodiment is the second embodiment wherein the dimerizationcatalyst comprises a Ti(IV)/AlEt₃ catalyst. Another embodiment is thesecond embodiment wherein the hydrogenation reactor operates at atemperature of less than 400° C., of less than 250° C., or of 100° C. to150° C. Another embodiment is the second embodiment wherein thehydrogenation reactor operates at a pressure above 1.7 MPa, of 0.7 MPato 8.2 MPa, of 0.7 MPa to 2.0 MPa, or of 1.0 MPa to 2.0 MPa. Anotherembodiment is the second embodiment wherein the hydrogenation catalystcomprises a Ni-alumina, Pd—C, Raney-Ni, Co, or Pt catalyst, or anycombination thereof.

A third embodiment is a method of producing liquefied petroleum gascomprising: contacting, in a carbonylation reactor, a carbonylation feedstream comprising ethanol with carbon monoxide and a carbonylationcatalyst to produce a first reactor effluent stream comprising propionicacid; wherein the carbonylation feed stream is a product of microbialfermentation of a gaseous substrate; and contacting, in a hydrogenationreactor, the first reactor effluent stream and hydrogen with a catalystto produce a product stream comprising propane. Another embodiment isthe third embodiment wherein the carbonylation reactor operates at atemperature of 150° C. to 250° C. or of 180° C. to 225° C. Anotherembodiment is the third embodiment wherein the carbonylation reactoroperates at a carbon monoxide partial pressure of 0.2 MPa to 3.0 MPa, of0.2 MPa to 1.0 Mpa, or of 0.2 MPa to 0.3 MPa. Another embodiment is thethird embodiment wherein the carbonylation catalyst comprises a Rhcarbonyl catalyst with ethyl and iodide ligands. Another embodiment isthe third embodiment wherein the hydrogenation reactor operates at atemperature of 130° C. to 200° C., of 140° C. to 190° C., of 150° C. to180° C., or of 150° C. to 170° C. Another embodiment is the thirdembodiment wherein the hydrogenation reactor operates at a pressure of2.0 MPa to 4.0 MPa, of 2.5 MPa to 3.5 MPa, or of 2.7 to 3.3 MPa. Anotherembodiment is the third embodiment wherein the hydrogenation catalystcomprises a Pd/Re/C catalyst.

A fourth embodiment is a liquified petroleum gas product produced by themethod of any one of the previous embodiments.

What is claimed is:
 1. A method of producing liquefied petroleum gascomprising: (a) producing a dehydration feed stream comprising ethanoland isopropanol by microbial fermentation of a gaseous substratecomprising CO, CO₂, CH₄, or any mixture thereof, wherein the dehydrationfeed stream has a water content of less than 30 wt %; (b) contacting, ina dehydration reactor, the dehydration feed stream with a dehydrationcatalyst to produce a first reactor effluent stream comprising ethyleneand propylene; (c) separating a propylene stream from the first reactoreffluent stream and contacting the remainder in a dimerization reactorwith a dimerization catalyst to produce a second reactor effluent streamcomprising butene; and (d) contacting, in a hydrogenation reactor, theseparated propylene stream and the second reactor effluent stream andhydrogen with a hydrogenation catalyst to produce a product streamcomprising butane and propane.
 2. The method of claim 1, wherein thedehydration reactor operates at a temperature of from 100° C. to 500°C., of from 350° C. to 450° C., or of from 375° C. to 425° C.
 3. Themethod of claim 1, wherein the dehydration reactor operates at apressure of from 0.2 MPa to 2 MPa, of from 0.2 MPa to 1 MPa, or of from0.2 MPa to 0.7 MPa.
 4. The method of claim 1, wherein the dehydrationreactor operates at a whsv of from 1 h⁻¹ to 10 h⁻¹, of from 2 h⁻¹ to 8h⁻¹, or of 0.5 h⁻¹ to 2 h⁻¹.
 5. The method of claim 1, wherein thedehydration catalyst is selected from acidic alumina, aluminumphosphate, silica-alumina phosphate, amorphous silica-alumina,aluminosilicate, zirconia, sulfated zirconia, tungstated zirconia,tungsten carbide, molybdenum carbide, titania, sulfated carbon,phosphated carbon, phosphated silica, phosphated alumina, acidic resin,heteropolyacid, inorganic acid, and any combination thereof.
 6. Themethod of claim 1, wherein the dimerization reactor operates at atemperature of from 10° C. to 150° C., of from 24° C. to 135° C., offrom 38° C. to 121° C., or of from 50° C. to 60° C.
 7. The method ofclaim 1, wherein the dimerization reactor operates at a pressure of 0.7MPa to 6.9 MPa, of 2.4 MPa to 4.8 MPa, of 2.8 MPa to 3.4 MPa, or of 2.0MPa to 2.7 MPa.
 8. The method of claim 1, wherein the dimerizationcatalyst comprises an ionic liquid catalyst.
 9. The method of claim 1,wherein the dimerization catalyst comprises a co-catalyst or a promoter.10. The method of claim 1, wherein the dimerization catalyst comprises aTi(IV)/AlEt3 catalyst.
 11. The method of claim 1, wherein thehydrogenation reactor operates at a temperature of less than 400° C., ofless than 250° C., or of 100° C. to 150° C.
 12. The method of claim 1,wherein the hydrogenation reactor operates at a pressure above 1.7 MPa,of 0.7 MPa to 8.2 MPa, of 0.7 MPa to 2.0 MPa, or of 1.0 MPa to 2.0 MPa.13. The method of claim 1, wherein the hydrogenation catalyst comprisesa Ni-alumina, Pd—C, Raney-Ni, Co, or Pt catalyst, or any combinationthereof.